Machine tool

ABSTRACT

The invention relates to a machine tool comprising feeding system to linearly feed a slide to be fed ( 5 ). Each feed gear comprises a first and a second feed mechanisms provided to be in a parallel manner and spaced apart from each other by a specified interval therebetween, wherein each feed mechanism comprises a linear feed-driving means, a feed-moving body which engages with the feed-driving means and moves along the feed-driving means, and a position sensor to detect positions of the feed-moving body along the feed-driving means. Each feed gear further comprises a first and a second support mechanisms respectively connected to each feed-moving body of the first and the second feed mechanisms with rotatably supporting the slide to be fed ( 5 ), and a controller ( 60 ) for controlling operations of the first and the second feed mechanisms respectively. In addition, at least either of support portions of the first and the second support mechanisms for rotatably supporting the slide to be fed ( 5 ) is provided to be movable in such a direction as separating from the other, rotating the slide to be fed ( 5 ) according to a difference in moving amount of the feed-moving bodies. Since the slide to be fed ( 5 ) is provided to be rotative, even such parts as having complicated surfaces can be easily machined.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a machine tool such as a lathe, amilling machine, a machining center etc. comprising feeding system tolinearly feed a tool rest, a tool post, a tool slide, a tool box and aslide to be fed such as a spindle head, a table etc.

2. Description of the Prior Art

An conventional general machine tool comprises feeding system composedof linear feed-driving means such as a ball screw etc., feed-movingbodies such as a ball nut etc. which engage with the feed-driving meansand move along them, and position sensors such as a rotary encoder etc.to detect positions of the feed-moving bodies along the feed-drivingmeans. The feeding system drive above-mentioned tool rest etc. and theslide such as the spindle head, the table etc. to move them linearly.

For example, the machining center comprises a table for installing anobject to be machined (hereinafter referred to as a work piece) thereto,a spindle which is rotatably supported and can hold a tool at a frontend portion thereof, and three pairs of feeding system which relativelymove the table and the spindle in the mutually orthogonal three axesdirections. Hence, through the relative displacement of the table andthe spindle in the above-mentioned three orthogonal axes directions bydriving the three pairs of feeding system, a three-dimensional machiningcan be realized for the work piece put on the table.

The above-mentioned three pairs of feeding system are disposed so thatthe each feed-driving means is mutually orthogonal, the table is drivenby the first feed gear provided with the horizontal feed-driving means,and the spindle is driven by the second and the third feeding systemwhose feed-driving means are mutually orthogonal as well as at rightangles to feed-driving means of the first feed gear. Generally, one feedgear is formed of one feed-driving means, and the slide to be fed suchas above-mentioned table is driven by such feed gear and also guided bylinear guide mechanisms (for example a rolling guide and a sliding guideetc.) arranged at both sides of the feed-driving means, the slide movingalong the linear guide mechanisms.

There are work pieces not only having the comparatively simple worksurfaces such as a horizontal surface and a perpendicular surface butalso having complicated surfaces that need complex machining such as aninclined surface and a curved surface.

However, in the conventional machine tool comprising above-mentionedfeeding system, since the spindle is driven so that it executes aparallel movement in a three-dimensional space with keeping a previouslyset posture thereof, that is to say, since it is impossible to swing thespindle in such a manner that a spindle center obliquely crosses feeddirections of the feeding system, the work piece having above-mentionedcomplicated surface cannot be machined.

For solving this problem, such a machining center as shown in FIG. 6 hasbeen developed. As shown in FIG. 6, a machining center 100 comprises abed 101, a pair of columns 102 and 102 respectively erected from bothsides of the bed 101, and a cross beam 103 horizontally linked withupper end portions of the column 102 and 102.

A table 105 which is driven by the first feed gear (not shown) havingabove-mentioned construction and reciprocally moves in the X-axisdirection indicated by an arrow (X) is mounted on the bed 101, and asaddle 106 which is driven by the second feed gear (not shown) andreciprocally moves in the Y-axis direction indicated by an arrow (Y) isdisposed at a front face 103 a of the cross beam 103, and a slide 107which is driven by the third feed gear (not shown) and reciprocallymoves in the Z-axis direction indicated by an arrow (Z) is disposed at afront of the saddle 106. A head holder 108 which is driven by a firstrotary feed gear (not shown) comprising a drive motor and a worm gearetc. and rotates in the direction of an arrow A is disposed at a frontof the feed slide 107. A spindle head 111 which is supported by asupport shaft 110, driven by a second rotary feed gear (not shown)comprising a drive motor etc., rotating in the direction of an arrow Bis disposed between a pair of support arms 109, 109 of the head holder108. The spindle head 111 rotatably supports a spindle 112 having afront end portion to hold a tool T and axially rotates the spindle 112by an appropriate drive means such as a built-in drive motor (not shown)etc.

Hence, above-mentioned each feed gear (not shown) and the drive means(not shown) are controlled in their operations by a controller 113.

In the machining center 100 comprising above-mentioned composingelements, the table 105 and the spindle 112 can be relatively moved inthe X-axis, Y-axis and Z-axis directions respectively by driving andcontrolling above-mentioned each feed gear (not shown) and the drivemeans (not shown) owing to the controller 113, furthermore, the spindle112 can swing so that the spindle center thereof obliquely crosses thedriving directions of the feeding system (not shown). Thus, the spindle112 can be linearly and curvilinearly moved in the three-dimensionalspace. Therefore, the work pieces having the complicated surfaces arecontinuously machined at a time with being fixed on the table 105.

However, there is another defect as described below in the machiningcenter 100 which enabled above-mentioned complicated machining.

The head holder 108 and the spindle head 111 are driven by the rotaryfeeding system comprising the drive motor and the worm gear etc.,rotating in the directions of the arrow A and the arrow B respectively,whereby needing complicated constructions thereof, as a result the sizeof a mechanism itself becomes large in view of strength thereof. Inaddition, since the rotary feeding system must be stored in a limitedspace, they cannot be produced easily, consequently a manufacturing costis heightened. It is also problem on accuracy that the rotary feedingsystem using the worm gear etc., have many error factors such as abacklash which disables a precise control of the head holder 108 and thespindle head 111.

It is a general advantage of the present invention to solveabove-mentioned problems and to provide an improved machine tool whichcan linearly move a tool rest etc. and a slide to be fed such as aspindle head, a table etc. and comprises feeding system to rotate theslide so as to obliquely cross the directions of above-mentioned linearmotions. A further advantage is to provide a machine tool comprisingabove-mentioned feeding system to machine work pieces having complicatedsurfaces.

SUMMARY OF THE INVENTION

The foregoing advantages are accomplished by the present machine toolthat comprises feeding system to linearly feed a slide to be fed. In themachine tool, each feed gear comprises a first and a second feedmechanisms which are provided in parallel manner spaced apart from eachother by a specified interval therebetween respectively comprising: alinear feed-driving means, a feed-moving body which engages with thefeed-driving means and moves along the feed-driving means and a positionsensor to detect positions of the feed-moving body along thefeed-driving means, a first and a second support mechanisms which arerespectively connected to each feed-moving body of the first and thesecond feed mechanisms and rotatably support the slide to be fed, and acontrol means to independently control the feed motions of the first andthe second feed mechanisms, wherein at least either of support portionsof the first and the second support mechanisms rotatably supporting theslide to be fed is disposed so as to move in such a direction as beingseparated from the other, and the slide to be fed is rotated on thebasis of a difference in moving amount of the feed-moving bodies.

According to the present invention, two feed-moving bodies can besynchronously moved by independently controlling the feed motions of thefirst and the second feed mechanisms, on the other hand, those twofeed-moving bodies can be moved in such a manner that there is adifference in moving amount therebetween. For synchronously moving twofeed-moving bodies, the slide to be fed can be moved in a parallelmanner, while for moving them such that there is a difference in movingamount therebetween, at least either of the support portions of thefirst and the second support mechanisms moves so as to separate from theother on the basis of the movements of the feed-moving bodies, as aresult the slide to be fed rotates within a plane including twofeed-driving means, consequently the slide to be fed moves with beingrotated in the feeding directions of the first and the second feedmechanisms.

As mentioned above, in the present invention, the slide to be fed can berotated. Therefore, even though a work piece has a complicated surface,it can be easily machined. In addition, since the slide to be fed can berotated by one feed gear, the structure of the feed gear itself is madesimple, consequently there is such an advantage that the machine tool inthe present invention can be produced easily in comparison with anconventional one, as a result a manufacturing cost can be lowered.

There is another advantage that the support portions in the presentinvention can be disposed so as to be linearly moved relative to theslide to be fed. Thus, a simple and precise mechanism to move thesupport portions can be attained.

In addition, the feed-driving means in above-mentioned present inventioncan be composed of a linear motor. The drive means with using theconventional worm gear as described above have many error factors suchas a backlash, therefore the slide to be fed cannot be preciselyrotated. However, by using the linear motor, such error decreases,whereby the slide to be fed can be precisely rotated.

Furthermore, when the slide to be fed is provided with a tool holdmechanism to hold a tool, the tool can be linearly moved in the feedingdirections of the feeding system and also can be rotated, whereby it ispossible to machine the work piece having the complicated surface suchas a curved one.

Furthermore, the machine tool in the present invention can comprise apair of columns disposed in a parallel manner being spaced away fromeach other by a specified interval therebetween, a cross beam linkedwith the columns, and a table that is provided under the cross beam andis allowed reciprocating in orthogonal direction of the cross beam,wherein the first and the second feed mechanisms are disposed at a frontface of the cross beam, the slide is provided with the tool holdmechanism to rotatably hold the tool, and the tool hold mechanism ismovable across the feed-driving means. In such construction, the tableand the tool hold mechanism can be linearly moved in two-axialdirections of a moving direction of the table and a longitudinaldirection of the cross beam both of which are disposed at right anglesto each other, also can be linearly moved relative to such a directionas crossing above-mentioned two axes. In addition, the tool holdmechanism can be rotated within the plane including the first and thesecond feed mechanisms, whereby the work pieces having the complicatedsurfaces such as the curved ones etc. can be continuously machined at atime with being fixed on the table. Furthermore, when a circular tablewhich can be horizontally rotated is set on the table, it is alsopossible to continuously machine work pieces having more complicatedshapes at a time with being fixed on the table.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view illustrating a preferred machine toolconcerning the present invention.

FIG. 2 is a greatly enlarged front elevation illustrating a spindle headand a cross beam of the machine tool shown in FIG. 1.

FIG. 3 is a cross-sectional view taken in the direction indicated by thearrow I—I shown in FIG. 2.

FIG. 4 is a cross-sectional view taken in the direction indicated by thearrow II—II shown in FIG. 2.

FIG. 5 is a cross-sectional view taken in the direction indicated by thearrow III—III shown in FIG. 2.

FIG. 6 is a perspective view illustrating an conventional machiningcenter.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Several embodiments of the present invention will hereinafter bedescribed with reference to the installed drawings.

As shown in FIG. 1, a machine tool according to the present invention isclassified into an elevation type machining center, comprising a bed 2,a pair of columns 3, 3 erected from both sides of the bed 2, a crossbeam 4 horizontally linked with upper end portions of the columns 3, 3,and a controller 60 for controlling operations of after-mentionedfeeding system etc. as basic composing elements.

A table 8 which is driven by the feeding system (not shown) andreciprocally moves in the X-axis direction indicated by an arrow (X) ismounted on the bed 2. A circular table 9 which is driven by a rotaryfeed gear (not shown) comprising a drive motor and a worm gear etc. androtating in the direction of an arrow C is mounted on the table 8.

As shown in FIG. 2 and FIG. 3, a front of the cross beam 4 is dividedinto an upper-side plane 4 a and a lower-side plane 4 b by means of aconcave area 4 c formed along the longitudinal direction of the front. Afirst feed mechanism 11 is provided along the upper-side plane 4 a,while a second feed mechanism 31 is provided along the lower-side plane4 b.

The first feed mechanism 11 comprises a linear magnet plate 12 in whichmagnetic poles excited to a N-pole and a S-pole are alternatelyarranged, a linear scale 16 placed along the magnet plate 12, a pair ofguide rails 14, 14 arranged along the magnet plate 12 and the linearscale 16 in such a manner as holding them, slide bearings 15, 15 whichrespectively engage with the guide rails 14, 14 and move along them, afeed-moving body 18 fixed to the slide bearings 15, 15, a stator 13fixed to the feed-moving body 18 so as to face the magnet plate 12, anda detection amplifier 17 fixed to the feed-moving body 18 so as to facethe linear scale 16.

The stator 13 constructs the linear motor together with the magnet plate12. An electric power is supplied from the controller 60. Magnetic poleson the stator 13 are excited to a N-pole and a S-pole by means of suchelectric power. The stator 13 and the feed-moving body 18 joinedtherewith are guided to the guide rails 14, 14 by an absorptive and arepulsive forces generated between the stator 13 and the fixed poles onthe magnet plate 12, moved to the Y1-axis direction indicated by anarrow (Y1). A scale on the linear scale 16 is read by the detectionamplifier 17, thus positions of the feed-moving body 18 on the linearscale 16 can be always detected by the detection amplifier 17.

The second feed mechanism 31 has the same construction as that of thefirst feed mechanism 11, comprising a magnet plate 32, a linear scale36, a pair of guide rails 34, 34, slide bearings 35, 35, a feed-movingbody 38, a stator 33, and a detection amplifier 37. As in the first feedmechanism 11, when an electric power is supplied to the stator 33 fromthe controller 60, an absorptive and a repulsive forces generate betweenthe stator 33 and fixed poles on the magnet plate 32, whereby the stator33 and the feed-moving body 38 joined therewith are guided to the guiderails 34 and 34, moved to the Y2-axis direction indicated by an arrow(Y2). Positions of the feed-moving body 38 on the linear scale 36 arealways detected by the detection amplifier 37.

As described above, the controller 60 is connected to the stators 13, 33and to the detection amplifiers 17, 37, receiving signals detected bythe detection amplifiers 17, 37, controlling the electric powerssupplied to the stators 13, 33 independently according to the signals,furthermore controlling the movements of the stator 13 and thefeed-moving body 18 joined therewith in the Y1-axis direction indicatedby the arrow (Y1) and the movements of the stator 33 and the feed-movingbody 38 joined therewith in the Y2-axis direction indicated by the arrow(Y2).

As shown in FIG. 4 and FIG. 5, the feed-moving body 18 of the first feedmechanism 11 and the feed-moving body 38 of the second feed mechanism 31are respectively provided with a first support mechanism 21 and a secondsupport mechanism 41, wherein the first support mechanism 21 and thesecond support mechanism 41 rotatably support a spindle head 5 as aslide to be fed.

The first support mechanism 21 comprises a support shaft 22 erected fromthe feed-moving body 18, a housing 24 which is rotatably connected tothe support shaft 22 through a bearing 23, guide rails 25, 25 whichguide the housing 24, and slide bearings 26, 26 which respectivelyengage with the guide rails 25, 25. The housing 24, the guide rails 25,25, and the slide bearings 26, 26 are arranged in a space 5 e formed inthe spindle head 5 at such a side thereof as facing the feed-moving body18. More precisely to say, the guide rails 25, 25 are perpendicularlyfixed to facing inside walls 5 f, 5 g of the space 5 e. The slidebearings 26, 26 which respectively engage with the guide rails 25, 25are fixed to outer surfaces 24 a, 24 b of the housing 24. According toabove-mentioned construction, the spindle head 5 is rotatably supportedby the first support mechanism 22. The support shaft 22, the bearing 23,the housing 24, and the spindle head 5 are in such a condition that theycan relatively move.

On the other hand, the second support mechanism 41 comprises a supportshaft 42 erected from the feed-moving body 38, and a bearing 43 which isheld inside of a hole 5 h formed in the spindle head 5 and is connectedto the support shaft 42, wherein the spindle head 5 is rotatablysupported by the support shaft 42 and the bearing 43.

As described above, a first feed gear 10 is composed of the first feedmechanism 11, the second feed mechanism 31, the first support mechanism21, the second support mechanism 41, and the controller 60 whichcontrols the operations of the first feed mechanism 11 and the secondfeed mechanism 31.

As shown in FIG. 1, FIG. 4, and FIG. 5, a space 5 a is formed so as tovertically thrust the spindle head 5. A spindle quill 6 is provided inthe space 5 a so as to move in the Z-axis direction indicated by anarrow (Z) in the direction along the length of the spindle head 5) withbeing driven by the second feed gear 50.

The second feed gear 50 comprises almost same composing elements as thefirst feed mechanism 11 and the second feed mechanism 31, comprising amagnet plate 51, a linear scale 53, a pair of guide rails 55, 55, slidebearings 56, 56, a stator 52, and a detection amplifier 54 etc.

The pair of guide rails 55, 55 are fixed perpendicular to facing insidewalls 5 b, 5 c of the space 5 a. The slide bearings 56, 56 which engagewith the guide rails 55, 55 are fixed to outer surfaces 6 a, 6 b of thespindle quill 6 respectively. The spindle quill 6 can be moved in theZ-axis direction indicated by the arrow (Z) with being guided by theguide rails 55, 55 as well as slide bearings 56, 56.

The magnet plate 51 and the linear scale 53 are fixed parallel to eachother and perpendicular to an inside wall 5 d of the space 5 a. Thestator 52 and the detection amplifier 54 are fixed parallel to eachother to an outer surface 6 c of the spindle quill 6 so that they facethe magnet plate 51 and the linear scale 53 respectively. An electricpower is supplied to the stator 52 from the controller 60 as in thefirst feed mechanism 11 and the second feed mechanism 31, whereby anabsorptive and repulsive forces generate between the stator 52 and fixedpoles of the magnet plate 51 so as to drive the stator 52 in the Z-axisdirection indicated by the arrow (Z), consequently the spindle quill 6joined with the stator 52 also moves in the Z-axis direction. Positionsof the spindle quill 6 on the linear scale 53 are always detected by thedetection amplifier 54. The controller 60 receives signals detected bythe detection amplifier 54, upon which controlling the electric powersupplied to the stator 52, controlling the movements of the stator 52and the spindle quill 6 joined therewith in the Z-axis directionindicated by the arrow (Z).

The spindle quill 6 rotatably supports a spindle 7 that can hold a toolT at a front end portion thereof. The spindle 7 can be axially rotatedby a built-in drive motor.

The same composing elements as the first feed gear 10 and the secondfeed gear 50 can be adopted to the feeding system (not shown) fordriving the table 8, while other mechanism composed of a ball screw, aball nut, and a servo motor etc. can be adopted, too. The feeding system(not shown), the rotary feed gear (not shown) to drive the circulartable 9, and the drive motor to rotate the spindle 7 are also to becontrolled in their operations by the controller 60. The machine tool 1also comprises a tool changing apparatus (not shown in particular)provided to appropriately change the tool T held by the spindle 7.

An operating condition of the machine tool 1 in this embodimentcomprising above-mentioned composing elements is described below withcentering on the operation of the first feed gear 10 as a characteristicelement. Hence, the spindle head 5 is in such a condition that thelongitudinal direction thereof is vertically kept in its initialcondition as shown in FIG. 2.

As described above, the controller 60 receives the signals detected bythe detection amplifiers 17, 37, controlling the electric powerssupplied to the stators 13, 33 respectively, controlling the movementsof the stator 13 and the feed-moving body 18 joined therewith in theY1-axis direction indicated by the arrow (Y1) as well as the movementsof the stator 33 and the feed-moving body 38 joined therewith in theY2-axis direction indicated by the arrow (Y2) respectively.

Therefore, the electric powers can be uniformly supplied from thecontroller 60 to the stators 13, 33. The spindle head 5 connected to thefirst support mechanism 21 and the second support mechanism 41 is movedparallel to the Y1-axis and Y2-axis directions with keeping its initialposture as described above when synchronously moving the stators 13, 33.

For example, in such a case that the electric power is supplied to thestator 13 so as to keep the position thereof while the electric power issupplied to the stator 33 so as to shift the position thereof and movesame in the plus Y2-axis direction, the spindle head 5 rotates in thedirection of an arrow A then stays in such a condition as shown byalternate long and two short dashes line in FIG. 2. This is because thespindle head 5 is rotatably supported by the first support mechanism 21and the second support mechanism 41. At this time, the spindle head 5rotates in the direction of the arrow A around the support shaft 42owing to the structures of the first support mechanism 21 and the secondsupport mechanism 41. On the other hand, the feed-moving body 18 and thespindle head 5 reciprocally rotate and move relative to the Z-axis,furthermore, the feed-moving body 18 and the feed-moving body 38separate from each other according to the moving amount of thefeed-moving body 38. This is because the support shaft 22 etc. of thefirst support mechanism 21 are disposed so as to move in relation to thespindle head 5 in the longitudinal direction thereof (in the Z-axisdirection).

On the contrary, in the case that the electric power is supplied to thestator 33 so as to keep the position thereof while the electric power issupplied to the stator 13 so as to shift the position thereof and movesame in the plus Y1-axis direction, the spindle head 5 rotates inreverse owing to the same action as described above.

When the electric power is supplied to each of the stator 13 and thestator 33 respectively such that moving rates thereof differ from eachother, there is a difference between the moving amounts of the stator 13and the stator 33 according to the supplied electric powers, whereby thespindle head 5 moves along the Y1-axis and the Y2-axis then rotates inthe direction of the arrow A according to above-mentioned difference inmoving amount of the stator 13 and the stator 33.

As mentioned above, the spindle head 5 can be moved parallel to theY1-axis and the Y2-axis or can be rotated in the direction of the arrowA, furthermore, such movement and rotation can be simultaneouslypromoted through the control of the electric powers supplied to thestators 13, 33.

In addition, the spindle quill 6 can be moved in the Z-axis directionindicated by the arrow (Z) by appropriately supplying the electric powerto the stator 52 of the second feed gear 50, while the table 8 can bemoved in the X-axis direction indicated by the arrow (X) by driving thefeeding system (not shown), furthermore the circular table 9 can berotated in the direction of the arrow C by driving the rotary feed gear(not shown).

Thus, in the machine tool 1 in this embodiment, the circular table 9 canbe moved in the direction of the arrow C and the X-axis direction, whilethe tool T can be moved in the Y1-axis and Y2-axis directions, the arrowA, as well as the Z-axis. Therefore, through the simultaneous drivingand controlling of the circular table 9 and the tool T, a work piece andthe tool T put on the circular table 9 and fixed thereto can besimultaneously moved relative to the directions of the arrow C, theX-axis, the Y1-axis, the Y2-axis and the arrow A, as well as the Z-axis.That is to say, the work piece and the tool T can be relatively moved ina three-dimensional space both in a linear and curvilinear manners.Thus, the work pieces can be continuously machined at a time with beingfixed on the circular table 9 even though they have complicated surfacesto be machined such as curved ones etc.

Since the spindle head 5 is rotated only by the first feed gear 10 whichplays a roll of a linear feed gear without using the rotary feed gearsuch as the drive motor and the worm gear, the structure of the rotarymechanism can be made simple, and besides the feed gear itself can bemade compact. Furthermore, the machine tool 1 in this embodiment can beeasily produced in comparison with the conventional machining center100, therefore there is such an advantage that the manufacturing costcan be decreased.

In addition, since the first feed gear is composed of the linear motor,there happen few errors such as a backlash etc. in comparison with therotary feed gear using the worm gear etc., therefore the spindle head 5can be precisely rotated, consequently a precise machining is enabled.

Moreover, since the support shaft 22 and the housing 24 of the firstsupport mechanism 21 are provided to be guided by the guide rails 25, 25as well as the slide bearings 26, 26 so as to relatively move linear tothe spindle head 5, the mechanism for moving the support shaft 22 andthe housing 24 can be made comparatively simple and precise.

It is to be understood that the characteristic structure of the presentinvention is not only practiced in the feeding system of the spindlehead 5 of the machining center as in this embodiment, but also carriedout in the feeding system of the table 8 as well as those of a tool postof a lathe, those of a spindle slide as other machine tools, besidesthose of a spindle head or a table of a milling machine in otherembodiments.

Furthermore, in this embodiment, the linear motor comprising the magnetplates 12, 32 and the stators 13, 33 is used for the first feed gear 10,while the linear motor comprising the magnet plate 51 and the stator 52is used for the second feed gear 50. However, it is to be understoodthat the invention is not limited in this embodiment. Therefore, thefeed mechanism comprising the ball screw, the ball nut, and the servomotor etc. can be used as each feed mechanism of the first feed gear 10and the second feed gear 50.

Industrial Field of the Invention

As described above, the machine tool with respect to the presentinvention is adaptable to machine parts having complicated surfaces suchas curved ones etc.

What is claimed is:
 1. In a machine tool provided with feeding system tolinearly feed a slide to be fed, each feed gear comprising: first andsecond feed mechanisms which are provided in a parallel manner spacedapart from each other by a specified interval therebetween, respectivelycomprising: a linear feed-driving means, a feed-moving body whichengages with the feed-driving means to move along the feed-drivingmeans, and a position sensor to detect positions of the feed-moving bodyalong the feed-driving means, first and second support mechanisms whichare respectively connected to each feed-moving body of the first and thesecond feed mechanisms and rotatably support the slide, and a controlmeans to control operations of the first and the second feed mechanismsrespectively, a pair of columns which are disposed in a parallel mannerbeing spaced away from each other by a specified interval therebetween,a cross beam which is horizontally linked with the columns, and a tablethat is provided under the cross beam and is allowed reciprocating inorthogonal direction of the cross beam, wherein at least either ofsupport portions of the first and the second support mechanisms forrotatably supporting the slide is provided to be moved in such adirection to separate from the other so as to rotate the slide accordingto a difference in moving amount of the feed-moving bodies, wherein thefirst and the second feed mechanisms are disposed at a front face of thecross beam, the slide is provided with the tool hold mechanism torotatably hold the tool, and the tool hold mechanism is movable acrossthe feed-driving means.
 2. A machine tool as set forth in claim 1characterized in that the support portions are provided to be relativelymovable linear to the slide.
 3. A machine tool as set forth in claim 1characterized in that the feed-driving means is composed of a linearmotor.
 4. A machine tool as set forth in claim 1 characterized in thatthe slide is provided with a tool hold mechanism for holding a tool. 5.A machine tool as set forth in claim 1 characterized in that ahorizontally rotatable circular table is disposed on the table.